The present invention relates to dust collectors and, more particularly, dust collectors of the type having a large volume filter bag and a removable collection bag.
Dust collectors are a desirable and quite frequently indispensable component of a woodworking shop. Unlike shop vacuum cleaners, in which a high speed universal motor (typically 15,000 rpm) drives a small diameter fan to generate a low volume air flow rate at a relatively high pressure rise, a dust collector utilizes a relatively low speed induction motor (typically 3,500 rpm) which drives a large diameter fan. Consequently, dust collectors generate a large volume air flow rate with a relatively moderate pressure rise. In addition, the filter area of most dust collectors is relatively large in comparison to that of shop vacuums. That feature, combined with the relatively low air velocity, results in the pressure differential across the filter media being relatively low, which highly increases the efficiency of dust removal.
The typical dust collector includes a housing having upper and lower openings, an internally or externally mounted blower, an externally mounted motor driving the blower, and a stand supporting the housing. A filter bag is attached to the upper opening and is made of a fabric material, such as cotton, which allows the air exhausted by the blower to exit the housing while retaining dust particles. The lower opening is covered by a collection bag which is made of plastic and is impermeable to air. The inlet to the blower is adapted to receive a large flexible hose (typically four to six inches in diameter) which usually is connected to a woodworking tool for purposes of removing sawdust and wood chips generated during a cutting operation.
The filter bag typically is shaped to provide a large surface area for air flow out of the housing, and is removable from the lower opening of the housing to facilitate its being emptied or changed. The support stand typically consists of a base which supports a collection bag and, in some cases, includes casters so that the dust collector may be moved to a desired location.
However, existing dust collectors have several disadvantages. For example, while the externally-mounted motor is free of the dust and chip laden environment of the interior of the housing, its weight tends to shift the center of gravity outwardly from the center of the housing, making the dust collector more susceptible to tipping. Furthermore, a dust collector having an externally mounted motor may have to be constructed to have a large "footprint"; that is, a protruding motor may result in the dust collector taking up more floor space than would be required for an internally mounted motor.
Another disadvantage of such dust collectors is that they typically include a single, large diameter hose which is attached either to a woodworking tool or to a floor intake. Accordingly, they are not designed to connect the dust collector to several pieces of equipment simultaneously.
Furthermore, the external location of large motors and blowers of such dust collectors causes them to be relatively noisy. In addition, the air exiting the blower within the housing may be at a relatively high velocity and tend to churn the dust and chips within the collection bag. This causes larger size chips and dust particles to adhere to the inside surface of the filter bag, reducing the effectiveness of the filter.
Accordingly, there is a need for a dust collector which has a center of gravity located near the center of the housing to promote stability of the collector, and which has a relatively small footprint, for its capacity, to improve portability and minimize space requirements. Furthermore, there is a need for a dust collector which can accept either a single large hose (e.g. four-inch diameter) or multiple hoses of smaller size (e.g. two and one half inch diameter) so that the collector may be used with several pieces of home workshop woodworking equipment or cleanup tools/accessories simultaneously. There is also a need for a dust collector that is relatively quiet in operation and in which the churning of the collected material by the blower exhaust is minimized. Finally, there is a need for a dust collector which utilizes standard plastic trash bags which can be changed quickly, making it appropriate for home use.